Design and analysis of an fMRI compatible haptic robot

Magnetic resonance (MR) compatible haptic devices have certain specific structural and operational properties, which are due to the magnetic field, and haptic requirements. Through the development of a haptic mechanism, which is compatible with a magnetic resonance environment, certain problems were solved, which are common to all robotic devices operating in an MR tunnel. This paper deals with the manipulability problem of a novel 3 DOF MR compatible haptic mechanism, considering limited space and its visualisation. An appropriate 3D visualisation method has been developed for analysing the manipulability characteristics of a haptic mechanism within an MR environment. Choosing a suitable driving system is one of the crucial design attributes for quality force transmission in haptic interfaces. This paper introduces certain adaptations, which have been done to enable the MR compatibility of a cable drive driven by an electric motor. It also presents the theoretical modelling of a cable drive for a 3 DOF MR compatible haptic mechanism, focusing on the hysteretic behaviour of polymeric cables.